47 lines
2.4 KiB
LLVM
47 lines
2.4 KiB
LLVM
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; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
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; RUN: opt -analyze -enable-new-pm=0 -scalar-evolution < %s | FileCheck %s
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; RUN: opt -disable-output "-passes=print<scalar-evolution>" < %s 2>&1 | FileCheck %s
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; The semanics of this example are a bit subtle. The loop is required
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; execute some number of times up to 1999. The compiler is free to reduce
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; the number of said iterations to zero (or any value in between) if desired,
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; but if it does so, the return value and the last value stored to G must
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; agree. For SCEV, this translates as widenable conditions preventing exact
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; exit counts from being computed, but not restricting max exit counts.
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; It's tempting to say that SCEV should return a precise exit count here, but
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; would result in miscompiles if transformations such as RLEV ran before
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; widening of the WC.
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define i32 @wc_max() {
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; CHECK-LABEL: 'wc_max'
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; CHECK-NEXT: Classifying expressions for: @wc_max
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; CHECK-NEXT: %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
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; CHECK-NEXT: --> {0,+,1}<%loop> U: [0,2000) S: [0,2000) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
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; CHECK-NEXT: %iv.next = add i32 %iv, 1
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; CHECK-NEXT: --> {1,+,1}<%loop> U: [1,2001) S: [1,2001) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
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; CHECK-NEXT: %widenable_cond3 = call i1 @llvm.experimental.widenable.condition()
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; CHECK-NEXT: --> %widenable_cond3 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
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; CHECK-NEXT: %exiplicit_guard_cond4 = and i1 %cond_1, %widenable_cond3
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; CHECK-NEXT: --> %exiplicit_guard_cond4 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
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; CHECK-NEXT: Determining loop execution counts for: @wc_max
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; CHECK-NEXT: Loop %loop: Unpredictable backedge-taken count.
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; CHECK-NEXT: Loop %loop: max backedge-taken count is 1999
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; CHECK-NEXT: Loop %loop: Unpredictable predicated backedge-taken count.
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;
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entry:
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br label %loop
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loop:
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%iv = phi i32 [0, %entry], [%iv.next, %loop]
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%iv.next = add i32 %iv, 1
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store i32 %iv, i32 *@G
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%cond_1 = icmp slt i32 %iv.next, 2000
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%widenable_cond3 = call i1 @llvm.experimental.widenable.condition()
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%exiplicit_guard_cond4 = and i1 %cond_1, %widenable_cond3
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br i1 %exiplicit_guard_cond4, label %loop, label %exit
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exit:
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ret i32 %iv
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}
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@G = external global i32
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declare i1 @llvm.experimental.widenable.condition()
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